Rotating substructure method based on component mode synthesis was proposed to reduce 3-D finite element rotor model. Planar (undamped) mode matrix was used to truncate the degrees of freedom of the substructure and the reduced gyroscopic matrix was got by multiplying a speed coefficient to the unit reduced ones. Compared with complex (damped) mode reduction method

it's no need to recalculate the truncation matrix

and it's more accurate than Guyan reduction method. 87% degrees of freedom of an aero-engine rotor model was reduced. The maximum critical speed error got from Campbell diagram is 0.04%. Unbalance response calculated by the reduced model is almost the same as the original's

and less than 20% RAM (random access memory) and computation time is used. All the results show that the proposed method is valid.